Head Injury Criterion (“HIC”) is a measure of the likelihood of head injury resulting from an impact. The HIC is used to assess safety related to occupants. Normally, this variable is derived from the acceleration/time history of an accelerometer mounted at the center of gravity of a dummy's head when the dummy is exposed to crash forces. As a result, HIC includes the effects of head acceleration and the duration of the acceleration (i.e., large accelerations may be tolerated if the duration is very short).
Conventionally, energy dissipation solutions in passenger seats have focused on allowing the passenger seatback to pivot forward in a controlled manner via features located in the lower back area of the passenger seatback that give way under a certain load. Generally, these features include metallic brackets with a designed shear area or shear bolts that are attached to the back diaphragm of the seat. These metallic brackets, however, may shear at inconsistent loads as a result of the composition of the metals and metal fatigue due to ongoing use. Shearing at inconsistent loads can lead to difficulties and often unacceptable HIC. In addition, when weight is a consideration, the use of metal for these brackets and other energy dissipation brackets can be prohibitive.